JPS61253530A - Control system for idle area of external memory - Google Patents

Abstract

PURPOSE:To shorten a searching time and to reduce the conversion into scraps with a hierarchical bit map by controlling the idle state with plural pairs of bits defined as a unit. CONSTITUTION:For the bit map 21 of level 0, the bits (x01-x0n) have the 1:1 correspondence to the areas (y1-yn) of fixed sizes forming an external memory 1 respectively with a bit defined as a unit. The bit values (0)2 and (1)2 means the presence and absence of an idle area respectively. The bit maps 22 and 23 of levels 1 and 2 define two bits as a unit and each of bits (x11-x1m and x21-x2l) corresponds to two units of the bit map of a level lower by 1 step. Then the bit values (00)2, (01)2, (10)2 and (11)2 mean that all areas are idle, an idle area exists at a level lower by 1 step, an idle area exists at a level lower by 2 steps and all areas are busy respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a management method for three areas of external storage of a computer, and can be widely applied in terms of capacity.

[Background of the invention]

Conventionally, one of the three management methods for the external storage of a computer
One known method is a bitmap method. This method has the advantage that the part (bitmap) that manages whether or not the external storage is empty is small, but when the capacity of the external storage increases, the performance of searching for empty space becomes a problem.

Hierarchizing bitmaps is an effective solution to this problem, but when layering bitmaps, the meaning of configuring a bitmap representing an empty state becomes complicated, which creates new problems.

That is, performance and fragmentation problems occur when reducing the search time in the vertical and horizontal directions of the hierarchy and searching the optimally sized sky are in conflict with each other.

n1ck/John J, "Operating Systems" by Donova, Computer Association, Computer Science Research Book Series, Assistant Professor, Department of Information Engineering, Kyoto University, Chapter 6, translated by Katsuo Ikeda There is information management.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an effective three-area management method for external storage to address the three-area search performance and fragmentation that are problems when allocating areas for large-capacity external storage.

[Summary of the invention]

In the present invention, a hierarchical bitmap that expresses an empty state using a plurality of bit pairs as one unit is applied to the management of three areas of external storage. The values of multiple pit pairs have the meanings shown below.

If the value of multiple bit pairs is 1→=0~l), and the level to which the multiple bit pairs belong is g(l=o~n), then the meaning of the value of multiple bit pairs is when (+)i=o , the level to which the multiple bit pairs belong is empty.

(2) When 0 < Z < ru, there is an empty level at (1;-i).

(5) When i=rb, there is no vacancy in the level to which the plural bit pairs belong.

Here, ru is the maximum value of multiple bit pairs.

When this hierarchical bitmap based on a plurality of bit pair representations is applied to the management of the three areas of external storage, the search in the vertical and horizontal directions can be shortened with respect to the search of the three areas. Another advantage is that it is easy to obtain three areas of optimal size.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIGS. 1 and 2 below.

This will be explained with reference to FIGS. 3, 4, and 5.

FIG. 1 is a diagram showing the configuration of an external storage and a bitmap, and the relationship between the two. 2 is the entire hierarchical bitmap, which is composed of bitmaps 21, 22, and 25 at each level.

21 is a level 00 bit map, where one bit is one unit, and each bit (!at~3:on) has a one-to-one correspondence with a fixed size area (y+~yrc) constituting the external storage 1. The bit values have the following meanings: 0 (0) 2: Empty.

(1) 2: No sky.

22 and 23 are bitmaps of level 1 and level 2, respectively, where one unit is a pair of two bits, and each bit (x11 to x+n, "21 to J2z) corresponds to two units of the bitmap at the next lower level. , the bit values have the following meanings.

(00)2: All empty.

(01)2: There is an empty level one level below.

(10) 2: There is a sky two levels below.

(11) 2: All are in use and there are no vacancies.

FIG. 2 is an example showing the state of the bitmap when the value of the spit pair is (00)2.
Indicates that there is a unit empty, 21 is one-to-one with external memory 1
This means that the external storage 1 has three areas of 4 units and 2 units.

FIG. 6 is an example showing the state of the bitmap when the value of the 2-bit pair is (11)2, and the value (11)2 of the bit pair of 23 and 22 is 4 units and 2
indicates that there is bit (1) 2 of the value in use for the unit;
This means that there are 4 units and 2 units of area in use in external storage 1.

Figure 4 is an example showing the state of the bitmap when the value of the 2-bit pair is (01)2. Indicates that there is space, 1 unit and 2 in external storage 1
This means that there are three areas of units.

Figure 5 shows an example of the state of the bitmap when the value of 2 bit pairs is (10)2, and the value of 23 bit pairs (
1 to 2 indicates that there is no vacancy in 22 and that there is vacancy below 22, that is, in 21, and means that there is 1 unit of empty space in external storage 1.

FIG. 6 is an example of an algorithm for searching three areas from a hierarchical bitmap. The input is T, r indicates which level of empty bit pair to allocate, and the content is level. The output is p, which indicates the position of the beginning of the three areas by the position of the level 0 bit pair. In FIG. 6, process 1 is initial value setting, and i and ) indicate the top bit pair of the highest level. k indicates the position of the last bit pair of each level, and the initial value is the position of the last bit pair of the highest level bitmap! (l corresponds to 23x2t in FIG. 1). Process 2 is to determine whether there is a sky where the value of x satisfies r. Process 6 indicates that when there is no vacancy as determined in process 2, x-ri is changed to the next bit pair. Processing 4 is a determination as to whether the bit pair at the end of the level has been processed. Process 5 is a determination as to whether x can be assigned as empty. Process 6 indicates changing the level of X to one level lower. Process 7 is the setting of output information when there are no three areas, and when P is -1, there is no output. Process 8 is the setting of output information when there are three areas, and p indicates the position of the bit at level 0 of the three areas.

〔Effect of the invention〕

According to the present invention, if the sky is searched from the top level of a hierarchical bitmap to the lower levels, there is an advantage that when searching the top level, it is possible to determine at which level the sky is located. This has the effect of reducing time. It also has the effect of alleviating fragmentation in that it can be determined whether there is space at a lower level.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the structure of an external storage and a bitmap according to an embodiment of the present invention and the relationship between the two, and FIG. Figures 3, 4, and 5 are explanatory diagrams of the relationship between the values of 2-bit pairs of a bitmap and the state of the bitmap, and Figure 6 is a block diagram showing an example of an algorithm for searching three areas from a hierarchical bitmap. It is. 1...External storage, Number...Level of hierarchical bitmap, r...Size to be allocated. ':, 11-

Claims (1)

[Claims] 1. A management method for three areas of external storage, which is characterized by managing empty states in a hierarchical bitmap, using multiple bit pairs as one unit.